Why are alpha particles positive?

Dec 29, 2014

An alpha particles is positively charged because it is essentially the nucleus of a Helium-4 atom.

A Helium-4 nucleus is composed of two protons, which are positively charged particles, and two neutrons, which have no electric charge.

A neutral He atom has a mass of four units (2 protons + 2 neutrons) and a net charge of zero because it has two electrons that balance the protons' positive charge; since an $\alpha \text{-particle}$ only has the protons and the neutrons, its charge will be +2$\to$+1 from each proton.